[PATCH 37/73] bitwise: Allow both regular casts and forced casts for restricted values

[Bart Van Assche <bvanassche@acm.org>]

From: Linus Torvalds <torvalds@linux-foundation.org>

Allow EXPR_FORCE_CAST as well as EXPR_CAST in restricted_value() when
checking whether an expression is a cast of 0 or ~0.

Support restricted constants defined with '__force' in kernel headers
(for example, '#define EPOLLIN (__force __poll_t)0x00000001') by
recognizing both forced and unforced casts of 0 and ~0 in
restricted_value().

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
[ bvanassche: Rewrite commit message in imperative mood, fix typo, unwrap
  EXPR_FORCE_CAST in restricted_value(), and extend
  validation/bitwise-all-bits-and-casts.c ]
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
---
 evaluate.c                              |  4 +--
 validation/bitwise-all-bits-and-casts.c | 46 +++++++++++++++++++++++--
 2 files changed, 45 insertions(+), 5 deletions(-)

diff --git a/evaluate.c b/evaluate.c
index b84eedbe4d33..ec02e5bbc4fe 100644
--- a/evaluate.c
+++ b/evaluate.c
@@ -443,7 +443,7 @@ static bool is_unsigned_restricted_or_int(struct symbol *sym)
 
 static int restricted_value(struct expression *v, struct symbol *type)
 {
-	if (v->type == EXPR_CAST) {
+	if (v->type == EXPR_CAST || v->type == EXPR_FORCE_CAST) {
 		struct symbol *ctype;
 		int cclass = classify_type(v->ctype, &ctype);
 		struct expression *leaf = v->cast_expression;
@@ -452,7 +452,7 @@ static int restricted_value(struct expression *v, struct symbol *type)
 			return 1;
 		if (restricted_value(v->cast_expression, ctype))
 			return 1;
-		while (leaf && leaf->type == EXPR_CAST)
+		while (leaf && (leaf->type == EXPR_CAST || leaf->type == EXPR_FORCE_CAST))
 			leaf = leaf->cast_expression;
 		if (leaf && leaf->type == EXPR_VALUE && leaf->value == 0)
 			return 0;
diff --git a/validation/bitwise-all-bits-and-casts.c b/validation/bitwise-all-bits-and-casts.c
index 01c8d84fcd67..ae0be1269ec4 100644
--- a/validation/bitwise-all-bits-and-casts.c
+++ b/validation/bitwise-all-bits-and-casts.c
@@ -1,6 +1,9 @@
+#define __force __attribute__((force))
+
 typedef unsigned long long __attribute__((bitwise)) be64;
 typedef unsigned int __attribute__((bitwise)) be32;
 typedef unsigned short __attribute__((bitwise)) be16;
+typedef signed int __attribute__((bitwise)) sbe32;
 
 static be32 test_all_bits(void)
 {
@@ -11,9 +14,11 @@ static be32 test_all_bits(void)
 	be32 e = +0;
 	be32 f = -0;
 	be32 g = (be32)0;
+	be32 h = (__force be32)0;
 	be32 i = (be32)~0;
+	be32 j = (__force be32)~0;
 
-	return a | b | c | d | e | f | g | i;
+	return a | b | c | d | e | f | g | h | i | j;
 }
 
 static be64 test_all_bits_64(void)
@@ -22,18 +27,22 @@ static be64 test_all_bits_64(void)
 	be64 b = ~0ULL;
 	be64 c = -1;
 	be64 d = (be64)0;
+	be64 e = (__force be64)0;
 	be64 f = (be64)~0;
+	be64 g = (__force be64)~0;
 
-	return a | b | c | d | f;
+	return a | b | c | d | e | f | g;
 }
 
 static be16 test_cross_cast_zero(void)
 {
 	be16 k = (be32)0;
+	be16 l = (__force be32)0;
 	be16 m = (be32)~0;
+	be16 n = (__force be32)~0;
 	be16 o = (unsigned short)~0;
 
-	return k | m | o;
+	return k | l | m | n | o;
 }
 
 static int test_ordered_compare(be32 x, be16 y)
@@ -54,7 +63,38 @@ static int test_ordered_compare(be32 x, be16 y)
 	return res;
 }
 
+static void test_bad_narrow_and_signed(sbe32 sx)
+{
+	be64 bad_u32 = ~0U;
+	be32 bad_u16 = (unsigned short)~0;
+	be32 bad_c16 = (be16)~0;
+	be32 bad_f16 = (__force be16)~0;
+	int bad_ord = (sx > 0);
+
+	(void)bad_u32;
+	(void)bad_u16;
+	(void)bad_c16;
+	(void)bad_f16;
+	(void)bad_ord;
+}
+
 /*
  * check-name: bitwise-all-bits-and-casts
  * check-command: sparse -Wbitwise $file
+ *
+ * check-error-start
+bitwise-all-bits-and-casts.c:68:24: warning: incorrect type in initializer (different base types)
+bitwise-all-bits-and-casts.c:68:24:    expected restricted be64 [usertype] bad_u32
+bitwise-all-bits-and-casts.c:68:24:    got unsigned int
+bitwise-all-bits-and-casts.c:69:25: warning: incorrect type in initializer (different base types)
+bitwise-all-bits-and-casts.c:69:25:    expected restricted be32 [usertype] bad_u16
+bitwise-all-bits-and-casts.c:69:25:    got unsigned short
+bitwise-all-bits-and-casts.c:70:25: warning: incorrect type in initializer (different base types)
+bitwise-all-bits-and-casts.c:70:25:    expected restricted be32 [usertype] bad_c16
+bitwise-all-bits-and-casts.c:70:25:    got restricted be16 [usertype]
+bitwise-all-bits-and-casts.c:71:25: warning: incorrect type in initializer (different base types)
+bitwise-all-bits-and-casts.c:71:25:    expected restricted be32 [usertype] bad_f16
+bitwise-all-bits-and-casts.c:71:25:    got restricted be16 [usertype]
+bitwise-all-bits-and-casts.c:72:24: warning: restricted sbe32 degrades to integer
+ * check-error-end
  */